With the recent diversification of services, a demand has arisen for greater volumes of data to be transmitted in a downlink. To meet this demand, M-ary modulation is used, in which a plurality of bits are arranged in one symbol. M-ary modulation is a modulation method whereby a plurality of bits are arranged in one symbol. Widely-known M-ary modulation methods include QPSK, in which 2 bits are arranged in one symbol, 8PSK, in which 3 bits are arranged in one symbol, and 16QAM, in which 4 bits are arranged in one symbol.
However, with M-ary modulation there is a problem in that the greater the number of bits arranged in one symbol, the smaller is the signal point interval in the signal space diagram, making reception signal point determination and likelihood calculation difficult, and resulting in deterioration of reception characteristics.